Synthesis of Magnesium Phosphorous Trichalcogenides and Applications in Photoelectrochemical Water Splitting
Jan Paštika, Filipa M. Oliveira, Vlastimil Mazánek, Zdeněk Sofer, Rui Gusmão
Abstract
Abstract Promising applications of metal phosphorous trichalcogenides (M 2 P 2 X 6 or MPX 3 ) have been predicted in optoelectronics, photoelectrocatalysis, and water‐splitting reactions, mainly due to its wide bandgap. Transition metals are widely used in the synthesis of MPX 3 , however, divalent cations of alkaline earth metals can also be constituents in MPX 3 2D layered structures. Herein, MgPX 3 (X = S, Se) are synthesized and their photoelectrochemical (PEC) activity is tested in the hydrogen evolution and oxygen evolution reaction (OER) regions under a wide range of wavelengths. MgPSe 3 photoelectrode shows the best PEC performance with a response of 1.6 ± 0.1 mA cm −2 under 420 nm. In the light‐assisted OER, a 200 mV improvement is obtained in the overpotential at 10 mA cm −2 for MgPSe 3 . The better performance of MgPSe 3 is consistent with its lower optical bandgap ( E g = 3.15 eV), as a result of the variation of electronegativity between selenide and sulfide.